tankless water heater questions

beckhamk · September 06, 2011, 10:25:25 AM

I am looking for recommendations on tankless water heaters. I would prefer to use propane tank less. Do all tankless wanter heaters still reuqire electric or are some setup to manual temprature knobs?

MountainDon · September 06, 2011, 12:47:01 PM

Many tankless gas heaters require electricity for the ignition system as they do not use a pilot light. Some have devices that use water flow to make the ignition work and do not require power. Others require power for their anti-freeze feature to work. Some also may have special warranty considerations depending on the water hardness. Best to read all the fine print on any unit that you look at.

September 06, 2011, 01:06:19 PM

Lots of options/configurations. I have a propane unit with no standing pilot light. It ignites by water flow and uses two D-cell batteries to provide the spark for the ignitor. Theoretically, it doesn't require electricity, but I wouldn't have water pressure without power to my water pump. If you have gravity water feed, then you could run it with no electricity, which would be really nice! It's inside, so it doesn't require heat to keep it from freezing like the exterior mounted units. There is a knob on mine that adjusts the water flow/volume, so by restricting that, the water is heated to a higher temperature. Some have provisions for cold air intake and some don't. Be sure to select the BTU capability based on your incoming water temperature and how many simultaneous hot water requirements you'll have, ie: 2 showers going at once, etc.

John Raabe · September 06, 2011, 01:40:20 PM

This site has some overview information that might be helpful:

http://www.tanklesswaters.com/

metolent · September 06, 2011, 02:37:55 PM

I have two different propane tankless water heaters - one is a really basic one with low flow (~2GPM at hottest setting) that I use in the small 12x16 guest cabin I built (John's plans) and then a Rinnai I just installed. Can't comment on the Rinnai since I haven't used it yet except to say that it requires 120VAC. The small one I have sounds like the one waggin has (which works great for the small bathroom with sink & shower and also a kitchen sink), uses 2 D-cell batteries for the ignition circuit. I didn't expect much from it since it was cheap cheap cheap, but it works great!

September 06, 2011, 03:42:02 PM

So what are these great cheap, D cell water heaters?

Rob_O · September 06, 2011, 05:46:02 PM

Quote from: Squirl on September 06, 2011, 03:42:02 PM
So what are these great cheap, D cell water heaters?

http://www.hotcampshowers.com/eccotemp_tankless_water_heaters

waggin · September 06, 2011, 06:52:02 PM

Newer version of the one I have:

http://www.lowes.com/ProductDisplay?partNumber=241453-1136-1600H+LP&langId=-1&storeId=10151&productId=1068691&catalogId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1

Mine is over 10 years old. I wouldn't call it great, as I'm still troubleshooting some issues, but it is working...usually.

Native_NM · September 06, 2011, 08:02:21 PM

In a retrofit situation, read the tech specs carefully. Tankless generally recommend 3/4" pipe or greater for best results.

September 06, 2011, 09:04:53 PM

I have been doing a lot of research about these, and I'm finding mixed reviews. I know that it is a neat idea, but there are 5-7 people in our house that might need to take showers at night. Not a problem now with our 50 gallon gas heater, but I would like to have the space back that it takes up in the pantry. Based on this, I'm not sure that we would be a good candidate. Thanks for all the info! Can anyone recommend a San Francisco plumbers?

considerations · September 06, 2011, 09:42:49 PM

I'll be able to stick my 2 cents worth in pretty soon....the plumbing should be functional by October and includes a Bosch, outside installed, tankless water heater.

OlJarhead · September 07, 2011, 08:58:42 AM

Quote from: considerations on September 06, 2011, 09:42:49 PM
I'll be able to stick my 2 cents worth in pretty soon....the plumbing should be functional by October and includes a Bosch, outside installed, tankless water heater.

Same one as listed above?

I've been planning on using a Bosch myself but am a little worried about the water pressure. I'll get 15-18psi from the cistern (gravity fed).

I also worry about using it in the winter but then I worry about ANY water usage in the winter! ha!

MountainDon · September 07, 2011, 09:23:20 AM

Is that a calculated pressure or an actual measured pressure? The one Bosch manual I have (125 series) states min pressure is 18 psi. The actual pressure developed by a head height can be less than calculated due to pipe friction.

SouthernTier · September 07, 2011, 11:26:01 AM

Quote from: MountainDon on September 07, 2011, 09:23:20 AM
Is that a calculated pressure or an actual measured pressure? The one Bosch manual I have (125 series) states min pressure is 18 psi. The actual pressure developed by a head height can be less than calculated due to pipe friction.

This is a great thread. The Eccotemp is just what I need. I will have gravity feed pressure. I was thinking that if you had a pressure (diaphragm) tank between the uphill cistern and the heater, then you wouldn't have to worry about the friction loss. The prsesure tank would equilabrate with the 18 psi (or whatever elevation you have) before you take your shower. So long as you don't use up the whole tank during your shower, you should still have 18 psi the whole time, depending on what type of tank you have.

But then again I am not a plumber.

The other solution would be to put a 12V RV pump just before the heater.

~~Anyone know what the minimum pressure for those eccotemp units is? Doesn't seem to list it on the website.~~

Edit: Eccotemp website not working right, but found manual here:

http://www.campingworld.com/includes/productSpecs/Instruction%20manual.pdf

In some places says needs 20-30 psi, elsewhere 40-50 psi. I'd need a 12V booster pump

September 07, 2011, 01:35:59 PM

@Don -- guesstimated pressure based on head height estimate -- gotta love that huh? I plan to test once I actually get my new pump in and can fill the cistern.

I've thought about a pressure tank or a 12v booster pump. Actually the booster pump should work right? As long as it has a steady volume of water? After all in the Tent trailer the water tank is under the pump yet it runs a shower just fine.

OlJarhead · September 07, 2011, 01:37:37 PM

I have a 55 gallon water drum (actually a recycled Coke drum) that I was thinking I could use for a reserve tank too, if I wanted. Maybe if it were insulated well enough to prevent freezing it could be filled when at the cabin and if it had a 12v pump installed in it to pump water to the tankless heater and rest of cabin then it wouldn't matter what the pressure at the cistern was....right?

SouthernTier · September 07, 2011, 02:40:29 PM

Quote from: OlJarhead on September 07, 2011, 01:35:59 PM
I've thought about a pressure tank or a 12v booster pump. Actually the booster pump should work right? As long as it has a steady volume of water? After all in the Tent trailer the water tank is under the pump yet it runs a shower just fine.

Again, I'm no plumber, but I think that one of those small pumps drawing water from a long tube going up to your cistern may cause too much of a vacuum on the inlet side, possibly leading to cavitation (damaging the pump) or just plain burning out the motor. I think the friction losses for shower-worthy flow through a long tube would be a lot more than just the hydraulic head from under a trailer to up to a shower head.

I was thinking of going with the pressure tank (pressurized by the hydraulic head from the uphill cistern) and using water directly from that for a faucet, etc. but for the shower, tee off another line from the tank and hook up a 12V pump just to run water to the heater and then the shower. Then the 12V pump would only be boosting the water pressure from 18 psi (or whatever was in the tank) up to enough to push through the heater and the shower nozzle, extending the life of the pump.

metolent · September 07, 2011, 02:42:38 PM

For the cheapie D-cell water heater, I went with the EZ101 from www.eztankless.com. I think I paid ~$120 or $130 for it last year. I have it mounted on the outside of my little guest house.

The Rinnai is the RL75iP I got from a place online called wholesale warehouse I think.

OlJarhead · September 07, 2011, 05:05:24 PM

I guess another way to do it is basically what you've suggested only just have the cistern keep the 55 gallon drum full so the 12vdc pump can pump out of it and into the cabin thereby providing water pressure for showers etc.

Might work

OlJarhead · September 07, 2011, 05:14:54 PM

http://forum.gon.com/showthread.php?t=481329
Found this thread when searching this topic.

It seems that maybe my idea for cabin water might actually have merit. All I'd need to do is bury the 55 gallon drum of water beneath the cabin (to keep the water from freezing in the winter) and insulate the pipes to the cabin (and drain them when not in use).

Might also need heat trace to keep them from freezing when we are there.

I think this would give me a full 55 gallons of water at all times in the small tank for the 12vdc pump and it would fill via gravity after the pump began to pump water to the shower, sink etc.

Thoughts?

September 07, 2011, 05:49:06 PM

My experience with the Shurflo RV type water pump is that they suck when it comes to lifting water. That is, they don't suck enough to provide decent output flow. They claim a 7 foot lift IIRC, but I was unhappy with the performance with only a three foot lift. That was my experience, maybe not ypical. I don't know anyone who has tried to lift water much with one.

My small utility pump also does not have much lift. I tried it with our buried water cistern and it did not work well and would not self prime with the tank depth. That's why we ended up with a hand pump to fill a small tank in the cabin. Our Shurflo feeds off the bottom outlet of that and provides plenty of pressure and flow for our uses, including a shower.

I would like to find an electric pump solution that did not involve requiring a submersible pump.

Squirl · September 08, 2011, 08:52:39 AM

I've had great luck with a submersible bilge pump. A personal observation, I believe bilge pumps are more efficient pumps because they are pushing the water up instead of pulling it, but that may just be my imagination. I was scrambling when I had a flooded foundation before the footing inspection. I ran to wally world and got the largest bilge pump they had on hand, 1200 gph. I was used to bilge pumps from boating and it was 12v so I didn't have to worry about a generator, I could just hook it up to the jeep. The pump is rated for 5 amps (60 watts). IIRC it cost around $40. It was a bigger pain to find a hose large enough to fit over the fitting on the pump. It was has a 3/4 outer diameter nub on the pump. The big box stores didn't have any hoses to match. I had to use 1.25" radiator hose from an auto parts store. The hose cost around $2 a foot for 7 feet. I hooked that up to a 10 foot 3/4 inch PVC pipe to pump the water away from the hole. It shot water out of the pipe with a 5 foot rise with very little loss in pressure. After the first hurricane, I ran it for almost ten hours straight and pumped thousands of gallons of muddy water. No problems. I expect to have to do the same after this hurricane. One of the downsides I could see is actual fitting the pump in the tank. I have 3 plastic 55 gallon drums that have 2" screw caps and the pump would never fit inside.

Squirl · September 08, 2011, 09:32:03 AM

Also as an addition, if burying a 55 gallon drum, I would at minimum go with steel drums over plastic. The plastic sidewalls of 55 gallon drums can collapse under the weight of the earth on the sides. Concrete would be better than all of the above, IMHO. Also, I noticed the original poster was in Georgia which has almost no frost depth. I assume you will be burying your tanks deeper. If it were anyplace other than under your cabin, I would worry about collapse strength of the top after being buried. I wouldn't want someone walking around and have the earth give way underneath them.

I don't really understand the sanitation issue. As long as the pump is cleaned when it is put in, it should stay clean. All organic matter that finds its way into the cistern will find its way into the line regardless of the pump.

davidj · September 08, 2011, 01:15:46 PM

Quote from: SouthernTier on September 07, 2011, 11:26:01 AM

~~Anyone know what the minimum pressure for those eccotemp units is? Doesn't seem to list it on the website.~~

Edit: Eccotemp website not working right, but found manual here:

http://www.campingworld.com/includes/productSpecs/Instruction%20manual.pdf

In some places says needs 20-30 psi, elsewhere 40-50 psi. I'd need a 12V booster pump

The low end for our pressure tank is 35psi and our Eccotemp keeps working (and it's at the end of 50ft of hose, so it's probably not getting the full 35psi when water's flowing).